Although brewers supply beer in bottles and cans as individual servings, a significant amount of beer is supplied in larger sized kegs (½ barrel, or 15.5 gal.) or half kegs (¼ barrel or 7.75 gallon) and 0.6 barrel (i.e., 5 gallon) kegs. Kegs are convenient for breweries, distributors and users in storing, chilling, and transporting beer. They are also a convenient means to dispense multiple servings through a tap attached to the keg. Kegs are particularly useful for dispensing beer in commercial establishments and at events.
A significant disadvantage of using kegs is that they are difficult to clean, sanitize, and reuse. The unused beer and protein inside the dark wet keg is a perfect environment for microorganisms to incubate and grow. In addition, the other components of the unused beer form “soil” and may contain “beerstone,” which is very difficult to remove. Microorganisms, soil and beerstone must be cleaned from the keg before reuse. Otherwise, there is a potential for risk of contamination, off-flavors and even health risks to the consumer. Beerstone harbors microorganisms, making the inside surface of the keg impossible to sanitize. Accordingly, the keg must be cleaned effectively, and the cleaning process itself should not leave a chemical residue. All of this must be accomplished in an economical manner.
Cleaning kegs in breweries has traditionally been accomplished by using hot water and alkaline liquid cleaning solutions comprised of sodium and/or potassium hydroxide. Sodium hydroxide (NaOH) and potassium hydroxide (KOH) utilize extremely high (e.g., 12-14) pH to hydrolyze (i.e., break down) soil to remove it. Sodium hydroxide is also known as “caustic soda” or “lye” and potassium hydroxide is known as “caustic potash.” In the last few decades, formulators have included surfactants (i.e., detergents) and sometimes chlorine bleach (i.e., sodium hypochlorite) or hydrogen peroxide along with the caustic to assist wetting and protein removal. Caustic cleaning solutions are used in the brewery because they are relatively inexpensive, can be recycled (i.e., re-used) and do a good job of removing protein-based soils. They do not, however, address calcium and magnesium hard water scale deposits nearly as well as acidic cleaning solutions. Like steam cleaning, which is also employed in some keg cleaning operations, the use of caustics presents hazards to workers who must handle or come in contact with those chemicals.
A decade ago, craft brewers began using a new generation of non-caustic, alkaline, oxygenated cleaning solutions instead of using caustic. These powdered non-caustic alkaline cleaners are safer for employees than their caustic predecessors due to their lower pH at the point of use. But non-caustic cleaners tend to cost more per pound than caustics. Also, they do not remove, and perhaps even promote, beerstone. “beerstone” is a hard organo-metallic scale that deposits on fermentation equipment and is chiefly composed of calcium oxalate or (C2CaO4). Accordingly, many brewers still use caustic cleaners in conjunction with the non-caustic cleaners to obtain complete removal of protein soil and beerstone. Cleaning with acid can be used as well, but breweries either use caustic, then neutralize with acid, or use acid only as a remedial step to remove beerstone.
In addition to the foregoing considerations, the spent cleaning solution must be environmentally friendly when discharged. Even more preferably, the cleaning solution should be capable of being recycled, which minimizes environmental impact and decreases the cost of the cleaning operation.
Thus, a need exists for providing an improved means for cleaning kegs, other beer containers and brewery equipment that is effective, safe, inexpensive and environmentally friendly.